This circuit can be use to protect your ignition box from a faulty regulator.
“A crowbar circuit is an electrical circuit used for preventing an overvoltage or surge condition of a power supply unit from damaging the circuits attached to the power supply.
It operates by putting a short circuit or low resistance path across the voltage output (Vo), like dropping a crowbar across the output terminals of the power supply.
Crowbar circuits are frequently implemented using a thyristor, TRIAC, trisil or thyratron as the shorting device.
Once triggered, they depend on the current-limiting circuitry of the power supply or, if that fails, the blowing of the line fuse or tripping the circuit breaker.”
Source : Wiki
SCR crowbar:
TRIAC crowbar:
Video